Background

SGTA, small glutamine-rich tetratricopeptide repeat-containing protein A, is an ubiquitously expressed co-chaperone that binds directly to HSC70 and HSP70 and regulates their ATPase activity (1,2). SGTA is a 34 kDa protein that is rich in glutamine residues at its C terminus and contains three tandemly repeated TPR motifs (3). The TPR domain of SGTA shows sequence similarity to the TPR domains of Hop, CHIP, and TOM70 (4). The TPR domain of SGTA also interacts with HSP90 and was recently found to be a pro-apoptotic factor (5,6).